1. Field of the Invention
This invention relates to bonding glass for the assembly of a composite type magnetic head comprising a magnetic core consisting of ferromagnetic ferrite, such as Mn-Zn ferrite, and a non-magnetic ceramic slider. This invention also relates to a magnetic head with which the bonding glass is used and, more specifically, to a Metal-In-Gap (hereinafter called MIG) composite type magnetic head, wherein an Fe-Al-Si film is applied to at least one of the faces containing the gap.
2. Related Art
An MIG composite type magnetic head consists of, as shown in FIG. 1, a slider 12 provided with side rails 11, a magnetic core 14 embedded in a slit 13 positioned at the end of one of the side rails 11, and a glass section 15 fixing and holding the magnetic core 14 in place.
FIG. 2 is an enlarged explanatory perspective drawing of the magnetic core 14. Portions 21 and 22 consist of magnetic substances called a C-type core piece and an I-type core piece respectively, and are made of Mn-Zn ferrite or the like. Portion 23 is an Fe-Al-Si film applied to the I-type core piece 22.
When assembling a composite type magnetic head, as shown in FIG. 3, the magnetic core 14 is inserted into the slit 13 of the slider 12 and is temporarily fixed by a spring 31.
Then a glass rod 32 is placed on the slider 12 at the position shown in FIG. 3, where it is heated to a high temperature, causing the glass to melt and flow into the gaps 33 and 34 between the slider 12 and the magnetic core 14.
Nevertheless, if the aforementioned temperature is too high, the glass in the gap of the magnetic core 14 may become loose, causing the gap to widen or the magnetic characteristics of the Fe-Al-Si film 23 may deteriorate, resulting in deterioration of the overall magnetic head characteristics.
Consequently, it is necessary to use low-melting point glass for the assembly of magnetic heads. The inventor of the present invention has thus proposed a low-melting point bonding glass composed of
______________________________________ SiO.sub.2 : 4.5 to 8.5 wt %, B.sub.2 O.sub.3 : 4.5 to 9.5 wt %, Al.sub.2 O.sub.3 : 6 to 8 wt % and PbO: 77.5 to 82.5 wt %. ______________________________________
(Japanese Patent Laid-Open No. 35619/1990)
Nevertheless, although the melting point of the proposed low-melting point glass is low enough for assembly of magnetic heads, discoloration occurs under conditions of high temperature and high humidity.
Besides the proposed low-melting point bonding glass, other of bonding glass as shown in Table 1 have been proposed.
(Japanese Patent Laid-Open No. 124745/1990)
TABLE 1 ______________________________________ Glass Items A B C D E ______________________________________ PbO 54 49 49 45 55 TeO.sub.2 18 22 22 23 13 BiO.sub.2 13 17 17 12 16 B.sub.2 O.sub.3 8 9 8 10 8 SiO.sub.2 0 0 4 10 8 Al.sub.2 O.sub.3 7 3 0 0 0 Thermal expansion 109 104 105 100 110 coefficient (.times.10.sup.-7 /.degree.C.) Setting 460 440 450 490 450 temperature (.degree.C.) ______________________________________
Nevertheless, these other types of glass tend to be subject to cracking when used as bonding glass for assembly of composite type magnetic heads, due to their inadequate thermal expansion coefficient values.